Carburetor



Dec. 7, 1965 Filed Feb. 15, 1965 2 Sheets-Sheet 1 II HI A W 47 44 /47.6% 25 i? 3% an 0 43 I 1 /a I 42 i 75 k E F G. 2 M

INVENTORJ VERNON D. NEWMAN AGENT United States Patent 3,222,039CARBURETOR Vernon D. Newman, Normandy, and Charles E. Barry,

St. Louis, Mo., assignors to ACF Industries, Incorporated, New York,N.Y., a corporation of New Jersey Fiied Feb. 15, 1963, Ser. No. 258,8702 Claims. (Cl. 261-69) This invention is directed to the fuel system forautomotive vehicles and specifically is directed to an improvement in acarburetor for such a fuel system.

A type of carburetor for supplying an air and fuel mixture to anautomotive vehicle engine is one in which fuel is delivered to a mixtureconduit from a fuel reservoir in the carburetor. The fuel is forced byatmospheric pressure on the surface of fuel within the fuel reservoirthrough a main fuel passage to the mixture conduit where it flows intoan air stream and mixes with the air in passing to the engine. Toprovide the optimum fuel air mixture ratio over the range of engineoperation, one type of carburetor utilizes in the main fuel system afuel jet or restriction of a predetermined size. A metering rod has afree graduated end positioned within this fuel jet. The graduations onthe metering rod vary from a large diameter to one of small diameter.These graduated portions of the metering rod are moved into the jet inresponse to engine requirements. Generally, when the engine is operatingat low speeds or at times where a minimum amount of fuel is required,the large diameter portion of the metering rod extends within the jet tominimize the flow of fuel to the main fuel passage. At other times whenthe maximum amount of fuel is required for proper engine operation, thesmallest portion of the metering rod extends through the jet to maximizefuel flow into the engine. In the type of carburetor, with which theinven tion is associated, a vacuum motor consisting of a diaphragm isattached to the metering rod to move the several graduated portions ofthe rod through the jet as required for engine operation. It has beenrecognized that it is necessary to maintain the free graduated end ofthe metering rod at a constant position within the jet. If this is notdone and during high speed operation of the engine when the flow of fuelthrough the jet is at a maximum, the free metering portion of the rodwill tend to whip around the jet from side to side and causeconsiderable turbulence and disruption of the fuel flow through the jet.This has resulted in an inconsistent flow of fuel during engineoperation so that the metering rod does not properly proportion the fuelto the engine. It has been found in the past that, if the metering rodis retained against one side of the jet in a fixed position, the flow offuel will remain more consistent at all speeds of engine operation. Itis known that the metering rod can be biased by a spring to one side ofthe jet to provide the optimum results. However, in the type ofcarburetor to be described the metering rod is suspended from a vacuummotor diaphragm through the main nozzle and through a fuel tube in sucha manner that it has been ditficult to position and support a spring inthe known way to bias the rod end against the side of the jet. For thesereasons a well known type of spring, mounted at the upper end of themetering rod, has been ineffective for biasing the lower end of themetering rod against the jet wall.

Therefore, it is an object of this invention to provide a simplified yeteffective spring bias for a metering rod.

Another object of the invention is to provide a simple spring biasingmeans which is easily accessible for servic ing to bias the metering rodagainst the edge of the metering jet.

The particular invention is one in which the graduated end of themetering rod extends through a jet into a fuel bowl of the carburetor insuch a manner that when the 3,222,039 Patented Dec. 7, 1965 fuel bowl isremoved, the metering rod end is easily accessible for servicing. Ahairpin spring is mounted with one end on the metering rod and anotherend on a fixed stud extending from the carburetor body for biasing themetering rod end against the jet wall and to provide consistent flow offuel through the jet.

FIGURE 1 is a plan view of a carburetor embodying the novel features ofthis invention.

FIGURE 2 is substantially a longitudinal sectional view of thecarburetor of FIGURE 1, which is shown mounted on an engine manifold andwith an air filter partially in section.

FIGURE 3 is a partial sectional view of the carburetor of FIGURE 1 andshowing a portion of the main fuel passage.

FIGURE 4 is an enlarged sectional view of a portion of FIGURE 3illustrating features of the invention.

FIGURE 5 is an enlarged plan view from below of the metering rodassembly of FIGURE 2, with the fuel bowl removed.

FIGURE 6 is a plan view of a metering rod spring, in accordance with theinvention.

The carburetor shown in FIGURES l and 2 consists essentially of acasting 10, which is formed with a fuel and air mixture conduit 12 and afuel bowl cover portion 14, from which is integrally formed a dependingaccelerating pump cylinder 16, an accelerating fuel passage 18 and afuel well structure 20. As shown, the mixture conduit 12 is arranged andaligned vertically during operation and is connected by a flange 13 tothe intake manifold M of an internal combustion engine E. In the lowerpart of the conduit 12 there is rotatably mounted a throttle valve 22fixed to a throttle shaft 24 journaled in appropriately alignedapertures of the body casting 10. A manually operable throttle lever 23is fixed to throttle shaft 24 to move the throttle 22 between open andclosed positions. In the upper portion of the fuel-air mixture conduit12 there is similarly mounted for rotational movement an unbalancedchoke valve 26 fixed to a choke valve shaft 28, which is also journaledin aligned apertures through the body casting 10. To the top of themixture conduit 12 is connected an air filter 29, partially shown insection in FIGURE 2. Between the upper and lower portions of the mixtureconduit 12 is formed a venturi or air flow restricting surface portion30. A small booster venturi 32 is formed integrally with the bodycasting 10 and has an inner venturi surface 34 coaxially aligned withthe mixture conduit 12 and the primary venturi surface 30.

A fuel bowl 36 is fixed beneath the fuel bowl cover 14 and is held withits rim tightly against a gasket fitted between the rim of the fuel bowl36 and matching portions of the fuel bowl cover 14. A float 4t) fixed toa float lever 43 is pivotally mounted from pin 42 journaled in adepending portion of fuel bowl cover 14. A lever arm 41 of the floatlever 43 abuts the lower end of a needle valve 44 having a tapered endextending into a valve seat of the inlet fitting 47 leading to the fuelbowl 36. The fitting 47 connects the carburetor to a fuel line .8. Fuelis forced under pressure by a pump 50 from a fuel tank 52, bothschematically shown, through the fuel line 48 and into the carburetorinlet fitting 47. With the fuel level in bowl 36 low, the float 40 islower and lever arm 43 allows valve 44 to be pressed by fuel pressure inline 48 to an open position. Fuel flows into the bowl 36 and when itreaches a predetermined level, the float lever arm 41 presses upwardlyagainst the needle valve 4 to close the inlet to the fuel bowl.

The lower end of the fuel well 20 is closed by a fitting 56 having acentral orifice 59 (FIGURE 4), which is carefully for-med to provide ametering jet for the flow of fuel from the fuel bowl 36 to the mixtureconduit 12. The upper end of the fuel well 20 intercepts a cross fuelpassage 58 directed downwardly into the secondary venturi structure 32.A nozzle fitting 60 is press-fitted into the end of passage 58 and hasone end thereof extending into the center of the secondary venturisurface 34. Press-fitted within the well 20 is a fuel emulsion tube 62having apertures 63 therethrough along its length, as shown in FIGURE 4.

A metering pin 66 is suspended within the fuel well 20. Pin 66 has, atits lower end 71, an intermediate reduced portion 68 positioned withinthe main fuel jet orifice 69 for operation in response to enginerequirements. Flow of fuelthrough the main jet 56 is controlled by' themetering rod 66 and in accordance with the rod portion 68 011 71 withinthe jet 56, as described below. The metering rod 66 is supported from aretainer 70 in which the upper end of rod 66 is frictionally engaged.

As shown in FIGURES 2 and 4, the metering rod 66 extends upwardly acrossthe main fuel passage 58 and into a recess 72 formed in the upperportion of the carburetor body casting 10. A diaphragm 76 is held on theretainer 70 by a cup washer 80 pressed tightly down over the upper endof retainer 70. A cylindrical bore 88 is formed in the upper surface ofthe carburetor casting and forms a continuation of the cavity 72. Thereis formed between bore 88 and cavity 72 an annular shoulder 90 having aconical surface. One end of a coil spring 85 is fitted into the cupwasher 80. A sheet metal thimbleshaped retainer 92 is placed within thebore 88 in a position shown in FIGURE 4 with the upper end of spring 85against the top of the retainer 92. A sheet metal eyelet-cup 89 ispress-fitted into the top of bore 88 and has a central re-entrantportion 87 which telescopes over the end of retainer 92 to tightly pressthe retainer 92 downwardly into the bore 88 so that a flanged rim 91 ofthe retainer 92 will force the periphery of diaphragm 76 onto thesurface of shoulder 90 with sufficient pressure to form a fuel-tightfit. Spring 85 is slightly compressed and will press the diaphragm andmetering rod retainer assembly downwardly into its lowest position, asshown in FIGURE 4.

An aperture 93 through the wall of thimble retainer 92 provides accessform bore 88 to the inside of retainer 92. As shown in FIGURE 3, apassage 94 is formed through the body casting 10 to the flange portion13 of the carburetor and opens at 25 into the mixing con duit andmanifold M below or downstream of the throttle 22. In this manner,passage 94 connects the space above the diaphram 76 to the manifoldpressure of the engine.

A passage 96 (FIGURE 2) is formed between the mixing conduit 12 from aregion between the choke valve 26 and the throttle valve 22 to extenddownwardly into the upper portion of well 20. Within the passage 96 ispress-fitted a restriction element 98 for controlling air flow throughpassage 96 into the well 20.

The operation of the main fuel circuits of the carburetor is as follows:Fuel from the fuel bowl 36 flows into the well structure 20, to fill itto the level of the fuel in the bowl. Upon the turning over of theengine, air is sucked through the air filter 29 into the mixture conduit12 and the intake manifold M. The flow of air through the boosterventuri 32 provides a sub-atmospheric pressure within the venturisurface 34 which extends back through the fuel passage 58 to the upperend of fuel well 20. The atmospheric pressure on the surface of the fuelwithin bowl 36 raises the fuel within the well and simultaneously air issucked through the restriction 98 and the bleed passage 96 into theupper portion of the fuel well. This air passes around and through theapertures 63 in the emulsion tube 62 to mix with the fuel and its vaporand to form an air-fuel emulsion. The emulsion is carried upwardly fromthe fuel well into the main fuel passage 58 and out the nozzle 60 toform a fuel and air mixture with the air passing through the mixtureconduit 12. When the engine is operating at low or idling speed suchthat the manifold vacuum is high, in the order of 18 inches of mercury,the diaphragm is forced by atmospheric pressure to its uppermostposition. This places the larger portion 71 of the rod 66 in the centralmetering portion of jet 56. A drop in manifold vacuum reduces the forceof atmospheric pressure on diaphragm 76 and spring presses rod 66downwardly a corresponding amount until the reduced rod portion 68 ispositoned within the jet to" permit an increase of fuel flow. As theshoulder between the rod portions 68 and 71 falls below the centralmetering portion of the jet passage 59, a maximum amount of fuel canflow through the jet. Manifold vacuum tends to drop as the throttle isopened from a closed position and thus the movement of the reducedportion 68 of rod 66 into the jet coincides with greater need for fuelas the throttle opens. The particular metering rod 66 substantiallyoperates as an off and on construction. That is, the fuel flow is eitherrestricted by the large portion 71 of the rod or is less restricted bythe reduced portion 68 of the rod and with little or no effect producedby the shoulder between rod portion 68 and rod portion 71. However,other types of metering rods may be used with a graduated thicknessbetween rod portions 68 and 71.

It has been found that during engine operation the fuel flow through themetering jet 56 will tend to move the metering rod end around and fromside to side within the jet opening. This effect is particular-1yextreme at high engine speeds when fuel flow is at a maximum. Then thefree end of rod 66 whips around the jet opening 59. Any change inposition of the metering rod during fuel flow through the jet providesan uneven flow of fuel so that the engine performance is not uniform. Ithas been found in the past that it is advantageous to bias the meteringrod 66 to one side of the jet so that it is retained always in oneposition during engine operation. In prior art structures, the biasingspring has been mounted at the upper portion of the metering rod toforce the lower end against the side of the jet. However, with theconstruction of the particular carburetor structure shown in FIGURE 4,it is diflicult to arrange a spring along the length of the metering rod66 to appropriately bias the end of the rod against the side of the jet56.

Accordingly, then, in accordance with this invention, a light spring isused for biasing the lower end of metering rod 66 against the meteringjet 56. Spring 95 consists of a light, thin, single strand hairpinspring fixed between the end of rod portion 71 and a fixed stud 97extending from the portion of casting 10. Spring 95 is formed with aseparate loop at each end. One loop 101 is fitted within a groove in therod end 71 and the other end loop 103 is fixed into a groove in the endof the stud 97. The bias of spring 95 is such as to move the end 71 ofthe rod 66 away from the stud 97 and against one side of the meteringjet 56, as shown in FIGURE 4. This spring bias eliminates any movementof the metering rod 66 freely from side to side in the pass-age 59.Thus, the flow of fuel through the jet 56 is maintained consistent.

The shape of the spring 95 is substantially that shown in FIGURE 6. Thespring itself may be made of 0.012" gauge music wire having a precoatingof zinc or cadmium to prevent corrosion. This particular material isnotlimiting and any appropriate material may be used for this spring.

Spring 95 has the advantage of maintaining the friction of the rod 66against the jet 56 to a minimum so as not to interfere with the actionof the diaphragm 76. The support of spring 95 is such that as the rod 66moves vertically, spring 95 will pivot around the stud 97. Thisarrangement minimizes friction between the spring 95 and rod 66 whichwould be greater if rod ,66 had to slide through the loop 101. Thusspring 95, being attached as described to the end 71 of the meteringrod, moves directly with the metering rod and is not forced to slideover a surface of the rod with a greater friction of movement.

The friction due to rotational movement of spring loop 103 in the groveof stud 97 is small in comparison to prior art arrangements.

We claim:

1. A carburetor comprising a body having an air and fuel mixture conduittherethrough, a main fuel passage within said carburetor body, meansforming a restricted jet portion of said fuel passage, a metering rodmovably mounted within said fuel passage and having a free end ofvarying thickness extending through said restricted jet passage portion,means attached to the other end of said rod for supporting said rod andfor providing reciprocable motion of said rod along its longitudinalaxis, and a spring biasing said free rod end against the Wall of saidjet passage portion, said spring consisting of a single strand of wireforming a single loop and having spaced outwardly biased ends each beingformed with an arcuate portion, a stud projecting from said carburetorbody in a direction substantially parallel to the longitudinal axis ofsaid metering rod and closed spaced therefrom on the downstream side ofsaid restricted jet portion, one arcuate end portion of said spring loopbeing fixed to said free rod end and the other arcuate end portionthereof being fixed to said stud, the movement of said rod along itslongitudinal axis moving the end portion of said spring fixed to the rodrelative to said end portion fixed to said stud whereby friction fromsaid spring upon movement of said metering rod is minimized.

2. A carburetor comprising a body having an air and fuel mixture conduittherethrough, a main fuel passage within said carburetor body, meansforming a restricted jet portion of said fuel passage, a metering rodmovably mounted within said fuel passage and having a free end ofvarying thickness extending through said restricted jet passage portion,diaphragm actuated means attached to the other end of said rod forsupporting said rod and for providing reciprocable motion of said rodalong its longitudinal axis, and a spring biasing said free rod endagainst the wall of said jet passage portion, said spring consisting ofa single strand of wire forming a single loop and having spacedoutwardly biased ends each being formed with an arcuate portion, a studprojecting from said carburetor body in a direction substantiallyparallel to the longitudinal axis of said metering rod and closelyspaced therefrom on the downstream side of said restricted jet passageportion, a first groove formed in said free metering rod end, a secondgroove formed in said stud, one arcuate end portion of said spring loopbeing fitted within said first groove of said free rod end and saidother arcuate end portion thereof being fitted within said second grooveof said stud, the movement of said rod along its longitudinal axismoving said spring end portion on the rod relative to the spring endportion on the stud whereby friction from said spring upon movement ofsaid metering rod is minimized.

References Cited by the Examiner UNITED STATES PATENTS 1,961,747 6/1934Ewart 251122 2,394,663 2/1946 Carlson et a1. 261-69 2,969,965 1/1961Braun 26169 3,025,877 3/1962 Buckay 25l61 3,084,865 4/1963 Fleer et a1.251-122 3,089,684 5/1963 Smith 261-69 HARRY B. THORNTON, PrimaryExaminer.

RONALD R. WEAVER, Examiner.

1. A CARBURETOR COMPRISING A BODY HAVING AN AIR AND FUEL MIXTURE CONDUITTHERETHROUGH, A MAIN FUEL PASSAGE WITHIN SAID CARBURETOR BODY, MEANSFORMING A RESTRICTED JET PORTION OF SAID FUEL PASSAGE, A METERING RODMOVABLY MOUNTED WITHIN SAID FUEL PASSAGE AND HAVING A FREE END OFVARYING THICKNESS EXTENDING THROUGH SAID RESTRICTED JET PASSAGE PORTION,MEANS ATTACHED TO THE OTHER END OF SAID ROD FOR SUPPORTING SAID ROD ANDFOR PROVIDING RECIPROCABLE MOTION OF SAID ROD ALONG ITS LONGITUDINALAXIS, AND A SPRING BIASING SAID FREE ROD END AGAINST THE WALL OF SAIDJET PASSAGE PORTION, SAID SPRING CONSISTING OF A SINGLE STRAND OF WIREFORMING SINGLE LOOP AND HAVING SPACED OUTWARDLY BIASED ENDS EACH BEINGFORMED WITH AN ARCUATE PORTION, A STUD PROJECTING FROM SAID CARBURETORBODY IN A DIRECTION SUBSTANTIALLY PARALLEL TO THE LONGITUDINAL AXIS OFSAID METERING ROD AND CLOSED SPACED THEREFROM ON THE DOWNSTREAM SIDE OFSAID RESTRICTED JET PORTION, ONE ARCUATE END PORTION OF SAID SPRING LOOPBEING FIXED TO SAID FREE ROD END AND THE OTHER ARCUATE END PORTIONTHEREOF BEING FIXED TO SAID STUD, THE MOVEMENT OF SAID ROD ALONG ITSLONGITUDINAL AXIS MOVING THE END PORTION OF SAID SPRING FIXED TO THE RODRELATIVE TO SAID END PORTION FIXED TO SAID STUD WHEREBY FRICTION FROMSAID SPRING UPON MOVEMENT OF SAID METERING ROD IS MINIMIZED.